Organic electroluminescent materials and devices

ABSTRACT

A compound having the structure of Formula I 
     
       
         
         
             
             
         
       
     
     is disclosed, where G a  has the structure 
     
       
         
         
             
             
         
       
     
     and G b  has the structure 
     
       
         
         
             
             
         
       
     
     In the structure of Formula I, Z is selected from Si and Ge; X a  and X b  are independently selected from the group consisting of O, S, and Se; the Y and Z atoms forming the six-membered rings in Formula I, G a , and G b  are each independently selected from C or N; each R 1 , R 2 , R a1 , R a2 , R b1 , and R b2  is independently selected from a variety of substituents; at least one R a1  is L a -A a ; at least one R b1  is L b -A b ; A a  and A b  are each independently selected from carbazole, dibenzofuran, dibenzothiophene, dibenzoselenophene, triphenylene, and nitrogen-substituted variants thereof, which are optionally further substituted; and L a  and L b  are each independently an organic linker. Formulations and devices, such as an OLEDs, that include the compound of Formula I are also described.

PARTIES TO A JOINT RESEARCH AGREEMENT

The claimed invention was made by, on behalf of, and/or in connectionwith one or more of the following parties to a joint universitycorporation research agreement: Regents of the University of Michigan,Princeton University, University of Southern California, and theUniversal Display Corporation. The agreement was in effect on and beforethe date the claimed invention was made, and the claimed invention wasmade as a result of activities undertaken within the scope of theagreement.

FIELD OF THE INVENTION

The present invention relates to compounds for use as hosts and devices,such as organic light emitting diodes, including the same.

BACKGROUND

Opto-electronic devices that make use of organic materials are becomingincreasingly desirable for a number of reasons. Many of the materialsused to make such devices are relatively inexpensive, so organicopto-electronic devices have the potential for cost advantages overinorganic devices. In addition, the inherent properties of organicmaterials, such as their flexibility, may make them well suited forparticular applications such as fabrication on a flexible substrate.Examples of organic opto-electronic devices include organic lightemitting devices (OLEDs), organic phototransistors, organic photovoltaiccells, and organic photodetectors. For OLEDs, the organic materials mayhave performance advantages over conventional materials. For example,the wavelength at which an organic emissive layer emits light maygenerally be readily tuned with appropriate dopants.

OLEDs make use of thin organic films that emit light when voltage isapplied across the device. OLEDs are becoming an increasinglyinteresting technology for use in applications such as flat paneldisplays, illumination, and backlighting. Several OLED materials andconfigurations are described in U.S. Pat. Nos. 5,844,363, 6,303,238, and5,707,745, which are incorporated herein by reference in their entirety.

One application for phosphorescent emissive molecules is a full colordisplay. Industry standards for such a display call for pixels adaptedto emit particular colors, referred to as “saturated” colors. Inparticular, these standards call for saturated red, green, and bluepixels. Color may be measured using CIE coordinates, which are wellknown to the art.

One example of a green emissive molecule is tris(2-phenylpyridine)iridium, denoted Ir(ppy)₃, which has the following structure:

In this, and later figures herein, we depict the dative bond fromnitrogen to metal (here, Ir) as a straight line.

As used herein, the term “organic” includes polymeric materials as wellas small molecule organic materials that may be used to fabricateorganic opto-electronic devices. “Small molecule” refers to any organicmaterial that is not a polymer, and “small molecules” may actually bequite large. Small molecules may include repeat units in somecircumstances. For example, using a long chain alkyl group as asubstituent does not remove a molecule from the “small molecule” class.Small molecules may also be incorporated into polymers, for example as apendent group on a polymer backbone or as a part of the backbone. Smallmolecules may also serve as the core moiety of a dendrimer, whichconsists of a series of chemical shells built on the core moiety. Thecore moiety of a dendrimer may be a fluorescent or phosphorescent smallmolecule emitter. A dendrimer may be a “small molecule,” and it isbelieved that all dendrimers currently used in the field of OLEDs aresmall molecules.

As used herein, “top” means furthest away from the substrate, while“bottom” means closest to the substrate. Where a first layer isdescribed as “disposed over” a second layer, the first layer is disposedfurther away from substrate. There may be other layers between the firstand second layer, unless it is specified that the first layer is “incontact with” the second layer. For example, a cathode may be describedas “disposed over” an anode, even though there are various organiclayers in between.

As used herein, “solution processible” means capable of being dissolved,dispersed, or transported in and/or deposited from a liquid medium,either in solution or suspension form.

A ligand may be referred to as “photoactive” when it is believed thatthe ligand directly contributes to the photoactive properties of anemissive material. A ligand may be referred to as “ancillary” when it isbelieved that the ligand does not contribute to the photoactiveproperties of an emissive material, although an ancillary ligand mayalter the properties of a photoactive ligand.

As used herein, and as would be generally understood by one skilled inthe art, a first “Highest Occupied Molecular Orbital” (HOMO) or “LowestUnoccupied Molecular Orbital” (LUMO) energy level is “greater than” or“higher than” a second HOMO or LUMO energy level if the first energylevel is closer to the vacuum energy level. Since ionization potentials(IP) are measured as a negative energy relative to a vacuum level, ahigher HOMO energy level corresponds to an IP having a smaller absolutevalue (an IP that is less negative). Similarly, a higher LUMO energylevel corresponds to an electron affinity (EA) having a smaller absolutevalue (an EA that is less negative). On a conventional energy leveldiagram, with the vacuum level at the top, the LUMO energy level of amaterial is higher than the HOMO energy level of the same material. A“higher” HOMO or LUMO energy level appears closer to the top of such adiagram than a “lower” HOMO or LUMO energy level.

As used herein, and as would be generally understood by one skilled inthe art, a first work function is “greater than” or “higher than” asecond work function if the first work function has a higher absolutevalue. Because work functions are generally measured as negative numbersrelative to vacuum level, this means that a “higher” work function ismore negative. On a conventional energy level diagram, with the vacuumlevel at the top, a “higher” work function is illustrated as furtheraway from the vacuum level in the downward direction. Thus, thedefinitions of HOMO and LUMO energy levels follow a different conventionthan work functions.

More details on OLEDs, and the definitions described above, can be foundin U.S. Pat. No. 7,279,704, which is incorporated herein by reference inits entirety.

SUMMARY OF THE INVENTION

According to one embodiment, a compound having the structure of FormulaI:

is provided, where G^(a) has the structure

and G^(b) has the structure

In the structure of Formula I:

Z is selected from Si and Ge;

X^(a) and X^(b) are independently selected from the group consisting ofO, S, and Se;

Y^(a1)-Y^(a3), Y^(a6)-Y^(a9), Y^(b1)-Y^(b3), Y^(b6)-Y^(b9),Z^(a2)-Z^(a6) and Z^(b2)-Z^(b6) are each independently selected from Cor N:

R¹ and R² each independently represent mono, di, tri, tetra, or pentasubstitution, or no substitution;

R^(a1) and R^(b1) each independently represent mono, di, tri, or tetrasubstitution, or no substitution;

R^(a2) and R^(b2) each independently represent mono, di, or trisubstitution, or no substitution;

each R¹, R², R^(a1), R^(a2), R^(b1), and R^(b2) is independentlyselected from the group consisting of hydrogen, deuterium, halide,alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino,silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl,acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl,sulfinyl, sulfonyl, phosphine, and combinations thereof;

at least one R^(a1) is L^(a)-A^(a);

at least one R^(b1) is L^(b)-A^(b);

A^(a) and A^(b) are each independently selected from the groupconsisting of carbazole, azacarbazole, dibenzofuran, dibenzothiophene,dibenzoselenophene, azadibenzofuran, azadibenzothiophene,azadibenzoselenophene, triphenylene and azatriphenylene which areoptionally further substituted, and wherein the substitution isoptionally fused to at least one benzo or azabenzo ring; and

L^(a) and L^(b) are each independently an organic linker.

According to another embodiment, a device comprising one or more organiclight emitting devices is also provided. At least one of the one or moreorganic light emitting devices can include an anode, a cathode, and anorganic layer, disposed between the anode and the cathode, wherein theorganic layer can include a compound of Formula I. The device can be aconsumer product, an electronic component module, an organiclight-emitting device, and/or a lighting panel.

According to yet another embodiment, a formulation containing a compoundof Formula I is provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an organic light emitting device.

FIG. 2 shows an inverted organic light emitting device that does nothave a separate electron transport layer.

FIG. 3 shows Formula I, G^(a), and G^(b) as disclosed herein.

DETAILED DESCRIPTION

Generally, an OLED comprises at least one organic layer disposed betweenand electrically connected to an anode and a cathode. When a current isapplied, the anode injects holes and the cathode injects electrons intothe organic layer(s). The injected holes and electrons each migratetoward the oppositely charged electrode. When an electron and holelocalize on the same molecule, an “exciton,” which is a localizedelectron-hole pair having an excited energy state, is formed. Light isemitted when the exciton relaxes via a photoemissive mechanism. In somecases, the exciton may be localized on an excimer or an exciplex.Non-radiative mechanisms, such as thermal relaxation, may also occur,but are generally considered undesirable.

The initial OLEDs used emissive molecules that emitted light from theirsinglet states (“fluorescence”) as disclosed, for example, in U.S. Pat.No. 4,769,292, which is incorporated by reference in its entirety.Fluorescent emission generally occurs in a time frame of less than 10nanoseconds.

More recently, OLEDs having emissive materials that emit light fromtriplet states (“phosphorescence”) have been demonstrated. Baldo et al.,“Highly Efficient Phosphorescent Emission from OrganicElectroluminescent Devices,” Nature, vol. 395, 151-154, 1998;(“Baldo-I”) and Baldo et al., “Very high-efficiency green organiclight-emitting devices based on electrophosphorescence,” Appl. Phys.Lett., vol. 75, No. 3, 4-6 (1999) (“Baldo-II”), which are incorporatedby reference in their entireties. Phosphorescence is described in moredetail in U.S. Pat. No. 7,279,704 at cols. 5-6, which are incorporatedby reference.

FIG. 1 shows an organic light emitting. The figures are not necessarilydrawn to scale. Device 100 may include a substrate 110, an anode 115, ahole injection layer 120, a hole transport layer 125, an electronblocking layer 130, an emissive layer 135, a hole blocking layer 140, anelectron transport layer 145, an electron injection layer 150, aprotective layer 155, a cathode 160, and a barrier layer 170. Cathode160 is a compound cathode having a first conductive layer 162 and asecond conductive layer 164. Device 100 may be fabricated by depositingthe layers described, in order. The properties and functions of thesevarious layers, as well as example materials, are described in moredetail in U.S. Pat. No. 7,279,704 at cols. 6-10, which are incorporatedby reference.

More examples for each of these layers are available. For example, aflexible and transparent substrate-anode combination is disclosed inU.S. Pat. No. 5,844,363, which is incorporated by reference in itsentirety. An example of a p-doped hole transport layer is m-MTDATA dopedwith F₄-TCNQ at a molar ratio of 50:1, as disclosed in U.S. PatentApplication Publication No. 2003/0230980, which is incorporated byreference in its entirety. Examples of emissive and host materials aredisclosed in U.S. Pat. No. 6,303,238 to Thompson et al., which isincorporated by reference in its entirety. An example of an n-dopedelectron transport layer is BPhen doped with Li at a molar ratio of 1:1,as disclosed in U.S. Patent Application Publication No. 2003/0230980,which is incorporated by reference in its entirety. U.S. Pat. Nos.5,703,436 and 5,707,745, which are incorporated by reference in theirentireties, disclose examples of cathodes including compound cathodeshaving a thin layer of metal such as Mg:Ag with an overlyingtransparent, electrically-conductive, sputter-deposited ITO layer. Thetheory and use of blocking layers is described in more detail in U.S.Pat. No. 6,097,147 and U.S. Patent Application Publication No.2003/0230980, which are incorporated by reference in their entireties.Examples of injection layers are provided in U.S. Patent ApplicationPublication No. 2004/0174116, which is incorporated by reference in itsentirety. A description of protective layers may be found in U.S. PatentApplication Publication No. 2004/0174116, which is incorporated byreference in its entirety.

FIG. 2 shows an inverted OLED 200. The device includes a substrate 210,a cathode 215, an emissive layer 220, a hole transport layer 225, and ananode 230. Device 200 may be fabricated by depositing the layersdescribed, in order. Because the most common OLED configuration has acathode disposed over the anode, and device 200 has cathode 215 disposedunder anode 230, device 200 may be referred to as an “inverted” OLED.Materials similar to those described with respect to device 100 may beused in the corresponding layers of device 200. FIG. 2 provides oneexample of how some layers may be omitted from the structure of device100.

The simple layered structure illustrated in FIGS. 1 and 2 is provided byway of non-limiting example, and it is understood that embodiments ofthe invention may be used in connection with a wide variety of otherstructures. The specific materials and structures described areexemplary in nature, and other materials and structures may be used.Functional OLEDs may be achieved by combining the various layersdescribed in different ways, or layers may be omitted entirely, based ondesign, performance, and cost factors. Other layers not specificallydescribed may also be included. Materials other than those specificallydescribed may be used. Although many of the examples provided hereindescribe various layers as comprising a single material, it isunderstood that combinations of materials, such as a mixture of host anddopant, or more generally a mixture, may be used. Also, the layers mayhave various sublayers. The names given to the various layers herein arenot intended to be strictly limiting. For example, in device 200, holetransport layer 225 transports holes and injects holes into emissivelayer 220, and may be described as a hole transport layer or a holeinjection layer. In one embodiment, an OLED may be described as havingan “organic layer” disposed between a cathode and an anode. This organiclayer may comprise a single layer, or may further comprise multiplelayers of different organic materials as described, for example, withrespect to FIGS. 1 and 2.

Structures and materials not specifically described may also be used,such as OLEDs comprised of polymeric materials (PLEDs) such as disclosedin U.S. Pat. No. 5,247,190 to Friend et al., which is incorporated byreference in its entirety. By way of further example, OLEDs having asingle organic layer may be used. OLEDs may be stacked, for example asdescribed in U.S. Pat. No. 5,707,745 to Forrest et al, which isincorporated by reference in its entirety. The OLED structure maydeviate from the simple layered structure illustrated in FIGS. 1 and 2.For example, the substrate may include an angled reflective surface toimprove out-coupling, such as a mesa structure as described in U.S. Pat.No. 6,091,195 to Forrest et al., and/or a pit structure as described inU.S. Pat. No. 5,834,893 to Bulovic et al., which are incorporated byreference in their entireties.

Unless otherwise specified, any of the layers of the various embodimentsmay be deposited by any suitable method. For the organic layers,preferred methods include thermal evaporation, ink-jet, such asdescribed in U.S. Pat. Nos. 6,013,982 and 6,087,196, which areincorporated by reference in their entireties, organic vapor phasedeposition (OVPD), such as described in U.S. Pat. No. 6,337,102 toForrest et al., which is incorporated by reference in its entirety, anddeposition by organic vapor jet printing (OVJP), such as described inU.S. Pat. No. 7,431,968, which is incorporated by reference in itsentirety. Other suitable deposition methods include spin coating andother solution based processes. Solution based processes are preferablycarried out in nitrogen or an inert atmosphere. For the other layers,preferred methods include thermal evaporation. Preferred patterningmethods include deposition through a mask, cold welding such asdescribed in U.S. Pat. Nos. 6,294,398 and 6,468,819, which areincorporated by reference in their entireties, and patterning associatedwith some of the deposition methods such as ink-jet and OVJD. Othermethods may also be used. The materials to be deposited may be modifiedto make them compatible with a particular deposition method. Forexample, substituents such as alkyl and aryl groups, branched orunbranched, and preferably containing at least 3 carbons, may be used insmall molecules to enhance their ability to undergo solution processing.Substituents having 20 carbons or more may be used, and 3-20 carbons isa preferred range. Materials with asymmetric structures may have bettersolution processability than those having symmetric structures, becauseasymmetric materials may have a lower tendency to recrystallize.Dendrimer substituents may be used to enhance the ability of smallmolecules to undergo solution processing.

Devices fabricated in accordance with embodiments of the presentinvention may further optionally comprise a barrier layer. One purposeof the barrier layer is to protect the electrodes and organic layersfrom damaging exposure to harmful species in the environment includingmoisture, vapor and/or gases, etc. The barrier layer may be depositedover, under or next to a substrate, an electrode, or over any otherparts of a device including an edge. The barrier layer may comprise asingle layer, or multiple layers. The barrier layer may be formed byvarious known chemical vapor deposition techniques and may includecompositions having a single phase as well as compositions havingmultiple phases. Any suitable material or combination of materials maybe used for the barrier layer. The barrier layer may incorporate aninorganic or an organic compound or both. The preferred barrier layercomprises a mixture of a polymeric material and a non-polymeric materialas described in U.S. Pat. No. 7,968,146, PCT Pat. Application Nos.PCT/US2007/023098 and PCT/US2009/042829, which are herein incorporatedby reference in their entireties. To be considered a “mixture”, theaforesaid polymeric and non-polymeric materials comprising the barrierlayer should be deposited under the same reaction conditions and/or atthe same time. The weight ratio of polymeric to non-polymeric materialmay be in the range of 95:5 to 5:95. The polymeric material and thenon-polymeric material may be created from the same precursor material.In one example, the mixture of a polymeric material and a non-polymericmaterial consists essentially of polymeric silicon and inorganicsilicon.

Devices fabricated in accordance with embodiments of the invention canbe incorporated into a wide variety of electronic component modules (orunits) that can be incorporated into a variety of electronic products orintermediate components. Examples of such electronic products orintermediate components include display screens, lighting devices suchas discrete light source devices or lighting panels, etc. that can beutilized by the end-user product manufacturers. Such electroniccomponent modules can optionally include the driving electronics and/orpower source(s). Devices fabricated in accordance with embodiments ofthe invention can be incorporated into a wide variety of consumerproducts that have one or more of the electronic component modules (orunits) incorporated therein. Such consumer products would include anykind of products that include one or more light source(s) and/or one ormore of some type of visual displays. Some examples of such consumerproducts include flat panel displays, computer monitors, medicalmonitors, televisions, billboards, lights for interior or exteriorillumination and/or signaling, heads-up displays, fully or partiallytransparent displays, flexible displays, laser printers, telephones,cell phones, tablets, phablets, personal digital assistants (PDAs),laptop computers, digital cameras, camcorders, viewfinders,micro-displays, 3-D displays, vehicles, a large area wall, theater orstadium screen, or a sign. Various control mechanisms may be used tocontrol devices fabricated in accordance with the present invention,including passive matrix and active matrix. Many of the devices areintended for use in a temperature range comfortable to humans, such as18 degrees C. to 30 degrees C., and more preferably at room temperature(20-25 degrees C.), but could be used outside this temperature range,for example, from −40 degree C. to +80 degree C.

The materials and structures described herein may have applications indevices other than OLEDs. For example, other optoelectronic devices suchas organic solar cells and organic photodetectors may employ thematerials and structures. More generally, organic devices, such asorganic transistors, may employ the materials and structures.

The term “halo,” “halogen,” or “halide” as used herein includesfluorine, chlorine, bromine, and iodine.

The term “alkyl” as used herein contemplates both straight and branchedchain alkyl radicals. Preferred alkyl groups are those containing fromone to fifteen carbon atoms and includes methyl, ethyl, propyl,isopropyl, butyl, isobutyl, tert-butyl, and the like. Additionally, thealkyl group may be optionally substituted.

The term “cycloalkyl” as used herein contemplates cyclic alkyl radicals.Preferred cycloalkyl groups are those containing 3 to 7 carbon atoms andincludes cyclopropyl, cyclopentyl, cyclohexyl, and the like.Additionally, the cycloalkyl group may be optionally substituted.

The term “alkenyl” as used herein contemplates both straight andbranched chain alkene radicals. Preferred alkenyl groups are thosecontaining two to fifteen carbon atoms. Additionally, the alkenyl groupmay be optionally substituted.

The term “alkynyl” as used herein contemplates both straight andbranched chain alkyne radicals. Preferred alkyl groups are thosecontaining two to fifteen carbon atoms. Additionally, the alkynyl groupmay be optionally substituted.

The terms “aralkyl” or “arylalkyl” as used herein are usedinterchangeably and contemplate an alkyl group that has as a substituentan aromatic group. Additionally, the aralkyl group may be optionallysubstituted.

The term “heterocyclic group” as used herein contemplates aromatic andnon-aromatic cyclic radicals. Hetero-aromatic cyclic radicals also meansheteroaryl. Preferred hetero-non-aromatic cyclic groups are thosecontaining 3 or 7 ring atoms which includes at least one hetero atom,and includes cyclic amines such as morpholino, piperdino, pyrrolidino,and the like, and cyclic ethers, such as tetrahydrofuran,tetrahydropyran, and the like. Additionally, the heterocyclic group maybe optionally substituted.

The term “aryl” or “aromatic group” as used herein contemplatessingle-ring groups and polycyclic ring systems. The polycyclic rings mayhave two or more rings in which two carbons are common to two adjoiningrings (the rings are “fused”) wherein at least one of the rings isaromatic, e.g., the other rings can be cycloalkyls, cycloalkenyls, aryl,heterocycles, and/or heteroaryls. Additionally, the aryl group may beoptionally substituted.

The term “heteroaryl” as used herein contemplates single-ringhetero-aromatic groups that may include from one to three heteroatoms,for example, pyrrole, furan, thiophene, imidazole, oxazole, thiazole,triazole, pyrazole, pyridine, pyrazine and pyrimidine, and the like. Theterm heteroaryl also includes polycyclic hetero-aromatic systems havingtwo or more rings in which two atoms are common to two adjoining rings(the rings are “fused”) wherein at least one of the rings is aheteroaryl, e.g., the other rings can be cycloalkyls, cycloalkenyls,aryl, heterocycles, and/or heteroaryls. Additionally, the heteroarylgroup may be optionally substituted.

The alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl, heterocyclic group,aryl, and heteroaryl may be optionally substituted with one or moresubstituents selected from the group consisting of hydrogen, deuterium,halogen, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy,amino, cyclic amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl,alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acid, ether,ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, andcombinations thereof.

As used herein, “substituted” indicates that a substituent other than His bonded to the relevant position, such as carbon. Thus, for example,where R¹ is mono-substituted, then one R¹ must be other than H.Similarly, where R¹ is di-substituted, then two of R¹ must be other thanH. Similarly, where R¹ is unsubstituted, R¹ is hydrogen for allavailable positions.

The “aza” designation in the fragments described herein, i.e.aza-dibenzofuran, aza-dibenzonethiophene, etc. means that one or more ofthe C—H groups in the respective fragment can be replaced by a nitrogenatom, for example, and without any limitation, azatriphenyleneencompasses both dibenzo[f,h]quinoxaline and dibenzo[f,h]quinoline. Oneof ordinary skill in the art can readily envision other nitrogen analogsof the aza-derivatives described above, and all such analogs areintended to be encompassed by the terms as set forth herein.

It is to be understood that when a molecular fragment is described asbeing a substituent or otherwise attached to another moiety, its namemay be written as if it were a fragment (e.g. phenyl, phenylene,naphthyl, dibenzofuryl) or as if it were the whole molecule (e.g.benzene, naphthalene, dibenzofuran). As used herein, these differentways of designating a substituent or attached fragment are considered tobe equivalent.

According to one embodiment, a compound having the structure of FormulaI:

is described, where G^(a) has the structure

and G^(b) has the structure

In the structure of Formula I:

Z is selected from Si and Ge;

X^(a) and X^(b) are independently selected from the group consisting ofO, S, and Se;

Y^(a1)-Y^(a3), Y^(a6)-Y^(a9), Y^(b1)-Y^(b3), Y^(b6)-Y^(b9),Z^(a2)-Z^(a6) and Z^(b2)-Z^(b6) are each independently selected from Cor N;

R¹ and R² each independently represent mono, di, tri, tetra, or pentasubstitution, or no substitution;

R^(a1) and R^(b1) each independently represent mono, di, tri, or tetrasubstitution, or no substitution;

R^(a2) and R^(b2) each independently represent mono, di, or trisubstitution, or no substitution;

each R¹, R², R^(a1), R^(a2), R^(b1), and R^(b2) is independentlyselected from the group consisting of hydrogen, deuterium, halide,alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino,silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl,acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl,sulfinyl, sulfonyl, phosphine, and combinations thereof;

at least one R^(a1) is L^(a)-A^(a);

at least one R^(b1) is L^(b)-A^(b);

A^(a) and A^(b) are each independently selected from the groupconsisting of carbazole, azacarbazole, dibenzofuran, dibenzothiophene,dibenzoselenophene, azadibenzofuran, azadibenzothiophene,azadibenzoselenophene, triphenylene and azatriphenylene which areoptionally further substituted, and wherein the substitution isoptionally fused to at least one benzo or azabenzo ring; and

L^(a) and L^(b) are each independently an organic linker.

In some embodiments, each one of Z^(a2)-Z^(a6) and Z^(b2)-Z^(b6) iscarbon. In some embodiments, each one of Y^(a1)-Y^(a3), Y^(a6)-Y^(a9),Y^(b1)-Y^(b3), and Y^(b6)-Y^(b9) is carbon.

In some embodiments, exactly one of Y^(a1)-Y^(a3) and Y^(a6)-Y^(a9) isnitrogen. In some embodiments, exactly one of Y^(b1)-Y^(b3) andY^(b6)-Y^(b9) is nitrogen.

In some embodiments, G^(a) and G^(b) are the same. In some embodiments,G^(a) and G^(b) are different.

In some embodiments L^(a), L^(b), or both, can be a direct connection(e.g., covalent bonds, such as single bonds, double bonds, or triplebonds). In some embodiments, linkers L^(a) and L^(b) are independentlyselected from the group consisting of a direct connection, alkyl, aryl,heteroaryl, and combinations thereof. In some embodiments, linkers L^(a)and L^(b) are independently selected from the group consisting of: adirect connection,

In the structures of L1-L23:

X¹ to X⁸ are C or N,

Y is N, O or S, and

each one of L1 through L23 may be further substituted by substituentsindependently selected from the group consisting of hydrogen, deuterium,halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy,amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl,heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile,isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinationsthereof.

In some embodiments, linkers L^(a) and L^(b) are independently selectedfrom the group consisting of: a direct connection,

which may be further substituted by substituents independently selectedfrom the group consisting of hydrogen, deuterium, halide, alkyl,cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl,alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl,carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl,sulfinyl, sulfonyl, phosphino, and combinations thereof.

In some embodiments, the compound is selected from the group consistingof:

In some embodiments, A^(a) is

which may be further substituted. In the structure of A^(a):

the substitution is optionally fused to at least one benzo or azabenzoring;

X^(a1) is selected from the group consisting of O, NR′, S, and Se;

Y^(a11)-Y^(a13) and Y^(a6)-Y^(a9) are each independently CR or N; and

each R and R′ is independently selected from the group consisting ofhydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl,alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl,alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester,nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphine, andcombinations thereof.

In some embodiments, A^(b) is

which may be further substituted. In the structure of A^(b):

the substitution is optionally fused to at least one benzo or azabenzoring;

X^(a1) is selected from the group consisting of O, NR′, S, and Se;

Y^(a11)-Y^(a13) and Y^(a6)-Y^(a9) are each independently CR or N; and

each R and R′ is independently selected from the group consisting ofhydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl,alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl,alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester,nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphine, andcombinations thereof.

In some embodiment, A^(a) is bonded from X^(a1), Y^(a11), Y^(a12), orY^(a13) to Y^(a6), Y^(a7), Y^(a8), or Y^(a9). In some embodiments, A^(b)is bonded from X^(b1), Y^(b11), Y^(b12), or Y^(b13) to Y^(b6), Y^(b7),Y^(b8), or Y^(b9).

In some embodiments, A^(a) and A^(b) are both carbazole. In someembodiments, A^(a) and A^(b) are both N-carbazole moieties. As usedherein, N-carbazole indicates that the X^(a1) for A^(a) or X^(b1) forA^(b) are nitrogen atoms that are bonded to the core silicon orgermanium moiety, i.e., Y^(a6), Y^(a7), Y^(a8), or Y^(a9) and Y^(b13) toY^(b6), Y^(b7), Y^(b8), or Y^(b9), respectively.

In some embodiments, A^(a) is connected to Y^(a6) and A^(b) is connectedto Y^(b6). In some embodiments, A^(a) is directly connected to Y^(a6)and A^(b) is directly connected to Y^(b6). As used herein, “connected”encompasses both a direct connection via a covalent bond (e.g., a singlebond or double bond) or a connection via covalent bonds to anintermediate linking moiety. In contrast, “directly connected” refers toa connection by a covalent bond to the exclusion of connections thatinclude an intermediate linking moiety.

In some embodiments, A^(a) is connected to Y^(a8) and A^(b) is connectedto Y^(b6). In some embodiments, A^(a) is directly connected to Y^(a8)and A^(b) is connected to Y^(b8).

In some embodiments, A^(a) is connected to Y^(a6), A^(b) is connected toY^(b6), and both A^(a) and A^(b) are N-carbazole. In some embodiments,A^(a) is directly connected to Y^(a6), A^(b) is directly connected toY^(b6), and both A^(a) and A^(b) are N-carbazole.

In some embodiments, A^(a) is connected to Y^(a8), A^(b) is connected toY^(b8), and both A^(a) and A^(b) are N-carbazole. In some embodiments,A^(a) is directly connected to Y^(a8), A^(b) is directly connected toY^(b8), and both A^(a) and A^(b) are N-carbazole.

According to another aspect of the present disclosure, a device thatincludes one or more organic light emitting device is also provided. Atleast one of the one or more organic light emitting devices can includean anode, a cathode, and an organic layer disposed between the anode andthe cathode. The organic layer can include a compound according toFormula I, and its variations as described herein.

In some embodiments, the organic layer can include one or more emitterdopants. The emitter dopants can be phosphorescent dopants, fluorescentdopants, or both. In some embodiments, the emitter is a phosphorescentdopant. In some embodiments, the organic layer is an emissive layer andthe compound of Formula I and its variations described herein is a host.

In some embodiments, the organic layer further comprises aphosphorescent emissive dopant, wherein the phosphorescent emissivedopant is a transition metal complex having at least one ligand or partof the ligand if the ligand is more than bidentate selected from thegroup consisting of:

In the ligand structures above, R_(a′), R_(b′), R_(c′), and R_(d′) mayrepresent mono, di, tri, or tetra substitution, or no substitution;R_(a′), R_(b′), R_(c′), and R_(d′) are independently selected from thegroup consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl,heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl,cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl,carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl,sulfonyl, phosphino, and combinations thereof; and two adjacentsubstituents of R_(a′), R_(b′), R_(c′), and R_(d′) are optionally joinedto form a fused ring or form a multidentate ligand.

In some embodiments, the organic layer is a blocking layer and thecompound of Formula I and its variations described herein is a blockingmaterial in the organic layer. In some embodiments, the organic layer isan electron transporting layer and the compound having Formula I and itsvariations described herein is an electron transporting material in theorganic layer.

In some embodiments, the device can be one or more of a consumerproduct, an electronic component module, an organic light emittingdevice, and a lighting panel.

In yet another aspect of the present disclosure, a formulation thatcomprises a compound according to Formula I and its variations describedherein is described. The formulation can include one or more componentsselected from the group consisting of a solvent, a host, a holeinjection material, hole transport material, and an electron transportlayer material, disclosed herein.

Combination with Other Materials

The materials described herein as useful for a particular layer in anorganic light emitting device may be used in combination with a widevariety of other materials present in the device. For example, emissivedopants disclosed herein may be used in conjunction with a wide varietyof hosts, transport layers, blocking layers, injection layers,electrodes and other layers that may be present. The materials describedor referred to below are non-limiting examples of materials that may beuseful in combination with the compounds disclosed herein, and one ofskill in the art can readily consult the literature to identify othermaterials that may be useful in combination.

HIL/HTL:

A hole injecting/transporting material to be used in the presentinvention is not particularly limited, and any compound may be used aslong as the compound is typically used as a hole injecting/transportingmaterial. Examples of the material include, but are not limited to: aphthalocyanine or porphyrin derivative; an aromatic amine derivative; anindolocarbazole derivative; a polymer containing fluorohydrocarbon; apolymer with conductivity dopants; a conducting polymer, such asPEDOT/PSS; a self-assembly monomer derived from compounds such asphosphonic acid and silane derivatives; a metal oxide derivative, suchas MoO_(x); a p-type semiconducting organic compound, such as1,4,5,8,9,12-Hexaazatriphenylenehexacarbonitrile; a metal complex, and across-linkable compound.

Examples of aromatic amine derivatives used in HIL or HTL include, butare not limited to the following general structures:

Each of Ar¹ to Ar⁹ is selected from the group consisting aromatichydrocarbon cyclic compounds such as benzene, biphenyl, triphenyl,triphenylene, naphthalene, anthracene, phenalene, phenanthrene,fluorene, pyrene, chrysene, perylene, azulene; group consisting aromaticheterocyclic compounds such as dibenzothiophene, dibenzofuran,dibenzoselenophene, furan, thiophene, benzofuran, benzothiophene,benzoselenophene, carbazole, indolocarbazole, pyridylindole,pyrrolodipyridine, pyrazole, imidazole, triazole, oxazole, thiazole,oxadiazole, oxatriazole, dioxazole, thiadiazole, pyridine, pyridazine,pyrimidine, pyrazine, triazine, oxazine, oxathiazine, oxadiazine,indole, benzimidazole, indazole, indoxazine, benzoxazole, benzisoxazole,benzothiazole, quinoline, isoquinoline, cinnoline, quinazoline,quinoxaline, naphthyridine, phthalazine, pteridine, xanthene, acridine,phenazine, phenothiazine, phenoxazine, benzofuropyridine,furodipyridine, benzothienopyridine, thienodipyridine,benzoselenophenopyridine, and selenophenodipyridine; and groupconsisting 2 to 10 cyclic structural units which are groups of the sametype or different types selected from the aromatic hydrocarbon cyclicgroup and the aromatic heterocyclic group and are bonded to each otherdirectly or via at least one of oxygen atom, nitrogen atom, sulfur atom,silicon atom, phosphorus atom, boron atom, chain structural unit and thealiphatic cyclic group. Wherein each Ar is further substituted by asubstituent selected from the group consisting of hydrogen, deuterium,halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy,amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl,heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile,isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinationsthereof.

In one aspect, Ar¹ to Ar⁹ is independently selected from the groupconsisting of:

wherein k is an integer from 1 to 20; X¹⁰¹ to X¹⁰⁸ is C (including CH)or N; Z¹⁰¹ is NAr¹, O, or S; Ar¹ has the same group defined above.

Examples of metal complexes used in HIL or HTL include, but are notlimited to the following general formula:

wherein Met is a metal, which can have an atomic weight greater than 40;(Y¹⁰¹-Y¹⁰²) is a bidentate ligand, Y¹⁰¹ and Y¹⁰² are independentlyselected from C, N, O, P, and S; L¹⁰¹ is an ancillary ligand; k′ is aninteger value from 1 to the maximum number of ligands that may beattached to the metal; and k′+k″ is the maximum number of ligands thatmay be attached to the metal.

In one aspect, (Y¹⁰¹-Y¹⁰²) is a 2-phenylpyridine derivative. In anotheraspect, (Y¹⁰¹-Y¹⁰²) is a carbene ligand. In another aspect. Met isselected from Ir. Pt, Os, and Zn. In a further aspect, the metal complexhas a smallest oxidation potential in solution vs. Fc⁺/Fc couple lessthan about 0.6 V.

Host:

The light emitting layer of the organic EL device of the presentinvention preferably contains at least a metal complex as light emittingmaterial, and may contain a host material using the metal complex as adopant material. Examples of the host material are not particularlylimited, and any metal complexes or organic compounds may be used aslong as the triplet energy of the host is larger than that of thedopant. While the Table below categorizes host materials as preferredfor devices that emit various colors, any host material may be used withany dopant so long as the triplet criteria is satisfied.

Examples of metal complexes used as host are preferred to have thefollowing general formula:

wherein Met is a metal; (Y¹⁰³-Y¹⁰⁴) is a bidentate ligand, Y¹⁰³ and Y¹⁰⁴are independently selected from C, N, O. P, and S; L¹⁰¹ is an anotherligand; k′ is an integer value from 1 to the maximum number of ligandsthat may be attached to the metal; and k′+k″ is the maximum number ofligands that may be attached to the metal.

In one aspect, the metal complexes are:

wherein (O—N) is a bidentate ligand, having metal coordinated to atoms Oand N.

In another aspect, Met is selected from Ir and Pt. In a further aspect,(Y¹⁰³-Y¹⁰⁴) is a carbene ligand.

Examples of organic compounds used as host are selected from the groupconsisting aromatic hydrocarbon cyclic compounds such as benzene,biphenyl, triphenyl, triphenylene, naphthalene, anthracene, phenalene,phenanthrene, fluorene, pyrene, chrysene, perylene, azulene; groupconsisting aromatic heterocyclic compounds such as dibenzothiophene,dibenzofuran, dibenzoselenophene, furan, thiophene, benzofuran,benzothiophene, benzoselenophene, carbazole, indolocarbazole,pyridylindole, pyrrolodipyridine, pyrazole, imidazole, triazole,oxazole, thiazole, oxadiazole, oxatriazole, dioxazole, thiadiazole,pyridine, pyridazine, pyrimidine, pyrazine, triazine, oxazine,oxathiazine, oxadiazine, indole, benzimidazole, indazole, indoxazine,benzoxazole, benzisoxazole, benzothiazole, quinoline, isoquinoline,cinnoline, quinazoline, quinoxaline, naphthyridine, phthalazine,pteridine, xanthene, acridine, phenazine, phenothiazine, phenoxazine,benzofuropyridine, furodipyridine, benzothienopyridine,thienodipyridine, benzoselenophenopyridine, and selenophenodipyridine;and group consisting 2 to 10 cyclic structural units which are groups ofthe same type or different types selected from the aromatic hydrocarboncyclic group and the aromatic heterocyclic group and are bonded to eachother directly or via at least one of oxygen atom, nitrogen atom, sulfuratom, silicon atom, phosphorus atom, boron atom, chain structural unitand the aliphatic cyclic group. Wherein each group is furthersubstituted by a substituent selected from the group consisting ofhydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl,alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl,alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester,nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, andcombinations thereof.

In one aspect, host compound contains at least one of the followinggroups in the molecule:

wherein R¹⁰¹ to R¹⁰⁷ is independently selected from the group consistingof hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl,arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl,heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylicacids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl,phosphino, and combinations thereof, when it is aryl or heteroaryl, ithas the similar definition as Ar's mentioned above. k is an integer from0 to 20 or 1 to 20; k′″ is an integer from 0 to 20. X¹⁰¹ to X¹⁰⁸ isselected from C (including CH) or N. Z¹⁰¹ and Z¹⁰² is selected fromNR¹⁰¹, O, or S.

HBL:

A hole blocking layer (HBL) may be used to reduce the number of holesand/or excitons that leave the emissive layer. The presence of such ablocking layer in a device may result in substantially higherefficiencies as compared to a similar device lacking a blocking layer.Also, a blocking layer may be used to confine emission to a desiredregion of an OLED.

In one aspect, compound used in HBL contains the same molecule or thesame functional groups used as host described above.

In another aspect, compound used in HBL contains at least one of thefollowing groups in the molecule:

wherein k is an integer from 1 to 20; L¹⁰¹ is an another ligand, k′ isan integer from 1 to 3.

ETL:

Electron transport layer (ETL) may include a material capable oftransporting electrons. Electron transport layer may be intrinsic(undoped), or doped. Doping may be used to enhance conductivity.Examples of the ETL material are not particularly limited, and any metalcomplexes or organic compounds may be used as long as they are typicallyused to transport electrons.

In one aspect, compound used in ETL contains at least one of thefollowing groups in the molecule:

wherein R¹⁰¹ is selected from the group consisting of hydrogen,deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy,aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl,aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile,isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinationsthereof, when it is aryl or heteroaryl, it has the similar definition asAr's mentioned above. Ar¹ to Ar³ has the similar definition as Ar'smentioned above. k is an integer from 1 to 20. X¹⁰¹ to X¹⁰⁸ is selectedfrom C (including CH) or N.

In another aspect, the metal complexes used in ETL include, but are notlimited to the following general formula:

wherein (O—N) or (N—N) is a bidentate ligand, having metal coordinatedto atoms O, N or N, N; L¹⁰¹ is another ligand; k′ is an integer valuefrom 1 to the maximum number of ligands that may be attached to themetal.

In any above-mentioned compounds used in each layer of the OLED device,the hydrogen atoms can be partially or fully deuterated. Thus, anyspecifically listed substituent, such as, without limitation, methyl,phenyl, pyridyl, etc. encompasses undeuterated, partially deuterated,and fully deuterated versions thereof. Similarly, classes ofsubstituents such as, without limitation, alkyl, aryl, cycloalkyl,heteroaryl, etc. also encompass undeuterated, partially deuterated, andfully deuterated versions thereof.

In addition to and/or in combination with the materials disclosedherein, many hole injection materials, hole transporting materials, hostmaterials, dopant materials, exciton/hole blocking layer materials,electron transporting and electron injecting materials may be used in anOLED. Non-limiting examples of the materials that may be used in an OLEDin combination with materials disclosed herein are listed in Table Abelow. Table A lists non-limiting classes of materials, non-limitingexamples of compounds for each class, and references that disclose thematerials.

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EXPERIMENTAL Synthesis Examples Synthesis of Compound 1

9-(2-Dibenzofuranyl)-9H-carbazole was prepared according to theliterature procedure (JP 2009267255). N-butyllithium (15 mL, 24 mmol,1.6 M in hexane) was added dropwise to 9-(2-dibenzofuranyl)-9H-carbazole(6.638 g, 20 mmol) in THF (200 mL) at −78° C. The reaction mixture waswarmed to 0° C. and stirred for 2 hours. The reaction mixture was thencooled to −78° C., and dichlorodiphenylsilane (1.69 mL, 8 mmol) wasadded dropwise. The reaction mixture was then allowed to warm to roomtemperature (20-25° C.) for approximately 12 hours. The reaction mixturewas then quenched at room temperature with H₂O (10 mL). The aqueous andorganic layers were separated. The aqueous layer was extracted withethyl acetate (×3), while the combined organic layer was washed withbrine, dried over MgSO₄, filtered and concentrated. The crude mixturewas then purified by flash column chromatography on silica gel withhexane-dichloromethane (9:1 to 5:5) to give 5.88 g (85% yield) of awhite solid. The white solid was re-purified by flash columnchromatography with hexane-dichloromethane (8:2) to give 1.35 g ofCompound 1 as white solid.

Synthesis of Compound 2 Synthesis ofBis(dibenzo[b,d]furan-4-yl)diphenylsilane

A 1 L 3-neck flask was charged with dibenzofuran (10 g, 59.5 mmol) andtetrahydrofuran (400 ml), and n-Butyllithium (1.6M solution in hexane,90 ml) was added dropwise into the reaction mixture at −78° C. Thereaction mixture was then stirred 1 hour and dichlorodiphenylsilane (5ml) was added dropwise. The reaction mixture was stirred at roomtemperature (20-25 degrees C.) for approximately 12 hours. The reactionmixture was quenched at room temperature by deionized water andextracted by dichloromethane. Magnesium sulfate was added to the organiclayer then filtered and the filtrate was evaporated to dryness. Theresidue was subjected to a column chromatography (SiO₂ gel, hexane) toyield the desired product, Bis(dibenzo[b,d]furan-4-yl)diphenylsilane (7g, 45%).

Synthesis of Bis(6-bromodibenzo[b,d]furan-4-yl)diphenylsilane

A 1 L 3-neck flask was charged withbis(dibenzo[b,d]furan-4-yl)diphenylsilane (7 g, 13.5 mmol) andtetrahydrofuran (400 ml). N-butyllithium (1.6M solution in hexane, 20ml) was added dropwise into the reaction mixture at −78° C. The reactionmixture was then maintained at 80° C. for 5 hours. The reaction mixturewas cooled to room temperature (20-25 degrees C.) and dibromomethane (6g) in tetrahydrofuran (10 ml) was added dropwise. The resulting mixturewas stirred at room temperature for about 12 hours and then quenched atroom temperature by deionized water and extracted by dichloromethane.Magnesium sulfate was added to the organic layer then filtered and thefiltrate was evaporated to dryness. The residue was then subjected to acolumn chromatography (SiO₂ gel, hexane) to yieldbis(6-bromodibenzo[b,d]furan-4-yl)diphenylsilane (5.7 g, 62%).

Synthesis of Compound 2

Bis(6-bromodibenzo[b,d]furan-4-yl)diphenylsilane (2.5 g, 3.7 mmol),carbazole (1.5 g, 9.0 mmol), cyclohexadiamine (0.17 g, 1.48 mmol), andpotassium phosphate tribasic (2.35 g, 11.1 mmol) were mixed in 150 mL ofxylene. The solution was bubbled with nitrogen for 15 min. Copper (I)iodide (0.14 g, 0.74 mmol) was then added and the resulting mixture washeated to reflux under nitrogen for approximately 12 hours. Aftercooling, the reaction mixture was filtered and concentrated. The residuewas then purified by column chromatography using hexane:dichloromethane(3:1) as eluent to yield 2.4 g (76%) of Compound 2.

Synthesis of Compound 4

9-(4-dibenzothienyl)-9H-carbazole was prepared according the literatureprocedure (US 20130241401). N-butyllithium (8.6 mL, 13.76 mmol, 1.6 M inhexane) was added dropwise to 9-(4-dibenzothienyl)-9H-carbazole (4.041g, 11.58 mmol) in THF (110 mL) at −78° C. The reaction mixture waswarmed to room temperature (20-25 degrees C.) and stirred for 5 hours.The reaction mixture was cooled to −78° C. before dichlorodiphenylsilane(0.97 mL, 4.61 mmol) was added dropwise to reaction mixture, which wasthen allowed to warm to room temperature over approximately 12 hours.The reaction mixture was then quenched at room temperature with H₂O (10mL). The aqueous and organic layers were separated. The aqueous layerwas extracted with ethyl acetate (×3), while the combined organic layerwas washed with brine, dried over MgSO₄, filtered, and concentrated. Thecrude mixture was purified by flash column chromatography on silica gelwith hexane-dichloromethane (9:1 to 7:3) to give 3.74 g (92% yield) of awhite solid. The white solid was recrystallised with toluene to give 1.7g of Compound 4.

Compound Data

The triplet energy of the synthesized compounds was calculated. Theresults are listed in Table 1 below.

TABLE 1 Compound Number Structure Triplet energy (nm) 1

424 2

420 4

416

Device Examples

Several OLED devices were produced to evaluate the compounds disclosedherein in an OLED environment. All device examples were fabricated byhigh vacuum (<10⁻⁷ Torr) thermal evaporation. The anode electrode was−800 Å of indium tin oxide (ITO). The cathode consisted of 10 Å of LiFfollowed by 1,000 Å of Al. All devices were encapsulated with a glasslid sealed with an epoxy resin in a nitrogen glove box (<1 ppm of H₂Oand O₂) and a moisture getter was incorporated inside the package. Inaddition to Compounds 1, 2, & 4, the following compounds were also usedto produce the device examples.

Device Example 1: The organic stack of the Device Examples listed inTable 2 consisted of sequentially, from the ITO surface, 100 Å of LG 101(purchased from LG Chem, Korea) as the hole injection layer (HIL), 250 Åof Compound A as the hole transporting layer (HTL), 300 Å of Compound 1doped with 20% of the emitter Compound B as the emissive layer (EML), 50Å of Compound C as the second electron transporting layer (ETL2) and 400Å of Alq₃ as the first electron transporting layer (ETL1).

Device Example 2, Device Example 3, Device Comparative Example 1, andDevice Comparative Example 2 were fabricated in the same way as DeviceExample 1, except Compound 2, Compound 3, Comparative Compound 1, andComparative Compound 2 were used as the hosts respectively.

The device data is summarized in Table 2 below. The lifetime data arenormalized to that of Comparative Example 1:

TABLE 2 At 20 mA/cm² 1931 CIE Em_(max) LT_(80%) Device Host x y [nm][AU] Example 1 Cmpd 1 0.174 0.389 474 158 Example 2 Cmpd 2 0.177 0.396474 250 Example 3 Cmpd 4 0.182 0.41 474 158 Comparative Comparative0.176 0.389 474 100 Example 1 Cmpd 1 Comparative Comparative 0.176 0.391474 108 Example 2 Cmpd 2

The data shows that devices with Compounds of Formula I with the4-position of the dibenzofuran or dibenzothiphene connected to thediphenylsilane as the host provided improved lifetime compared to theComparative Compounds with the 2-position of the dibenzofuran ordibenzothiphene connected to the diphenylsilane as the host. Forexample, Compound 1 and Comparative Compound 1 only differ in the4-position vs. 2-position linkage of the dibenzofuran. However, DeviceExample 1 (with Compound 1 as the host) has a lifetime measure LT₈₀ of158 whereas Comparative Device Example 1 (with Comparative Compound 1 asthe host) has LT_(80%) of 100 at a current density of 20 mA/cm². DeviceExample 2 exhibited even better lifetime values (2.5 times better thanthat of Comparative Example 1), by having the 4-position of thedibenzofuran connected to the silicon and the 6-position of thedibenzofuran connected the N of carbazole. The data suggests connectingthe 4-position of the dibenzofuran or dibenzothiphene to thediphenylsilane may enhance lifetime. Furthermore connecting the4-position of the dibenzofuran or dibenzothiphene to the diphenylsilaneand 6-position the dibenzofuran or dibenzothiphene to N-carabzoleprovides even more improved result.

It is understood that the various embodiments described herein are byway of example only, and are not intended to limit the scope of theinvention. For example, many of the materials and structures describedherein may be substituted with other materials and structures withoutdeviating from the spirit of the invention. The present invention asclaimed may therefore include variations from the particular examplesand preferred embodiments described herein, as will be apparent to oneof skill in the art. It is understood that various theories as to whythe invention works are not intended to be limiting.

1. A compound having the structure of Formula I:

wherein G^(a) has the structure

wherein G^(b) has the structure

wherein Z is selected from Si and Ge; wherein X^(a) and X^(b) areindependently selected from the group consisting of O, S, and Se;wherein Y^(a1)-Y^(a3), Y^(a6)-Y^(a9), Y^(b1)-Y^(b3), Y^(b6)-Y^(b9),Z^(a2)-Z^(a6) and Z^(b2)-Z^(b6) are each independently selected from Cor N; wherein R¹ and R² each independently represent mono, di, tri,tetra, or penta substitution, or no substitution; wherein R^(a1) andR^(b1) each independently represent mono, di, tri, or tetrasubstitution, or no substitution; wherein R^(a2) and R^(b2) eachindependently represent mono, di, or tri substitution, or nosubstitution; wherein each R¹, R², R^(a1), R^(a2), R^(b1), and R^(b2) isindependently selected from the group consisting of hydrogen, deuterium,halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy,amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl,heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile,isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphine, and combinationsthereof; wherein at least one R^(a1) is L^(a)-A^(a); wherein at leastone R^(b1) is L^(b)-A^(b); wherein A^(a) and A^(b) are eachindependently selected from the group consisting of carbazole,azacarbazole, dibenzofuran, dibenzothiophene, dibenzoselenophene,azadibenzofuran, azadibenzothiophene, azadibenzoselenophene,triphenylene and azatriphenylene which are optionally furthersubstituted, and wherein the substitution is optionally fused to atleast one benzo or azabenzo ring; and wherein L^(a) and L^(b) are eachindependently an organic linker.
 2. The compound according to claim 1,wherein each one of Z^(a2)-Z^(a6) and Z^(b2)-Z^(b6) is carbon.
 3. Thecompound according to claim 1, wherein each one of Y^(a1)-Y^(a3),Y^(a6)-Y^(a9), Y^(b1)-Y^(b3), and Y^(b6)-Y^(b9) is carbon.
 4. Thecompound according to claim 1, wherein exactly one of Y^(a1)-Y^(a3) andY^(a6)-Y^(a9) is nitrogen.
 5. The compound according to claim 1, whereinexactly one of Y^(b1)-Y^(b3) and Y^(b6)-Y^(b9) is nitrogen.
 6. Thecompound according to claim 1, wherein G^(a) and G^(b) are the same. 7.The compound according to claim 1, wherein G^(a) and G^(b) aredifferent.
 8. The compound according to claim 1, wherein linkers L^(a)and L^(b) are independently selected from the group consisting of adirect connection, alkyl, aryl, heteroaryl, and combinations thereof. 9.The compound according to claim 1, wherein linkers L^(a) and L^(b) aindependently selected from the group consisting of: a directconnection,

wherein X¹ to X⁸ are C or N, wherein Y is N, O or S, and wherein eachone of L1 through L23 may be further substituted by substituentsindependently selected from the group consisting of hydrogen, deuterium,halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy,amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl,heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile,isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinationsthereof.
 10. The compound according to claim 1, wherein linkers L^(a)and L^(b) are independently selected from the group consisting of: adirect connection,

which may be further substituted by substituents independently selectedfrom the group consisting of hydrogen, deuterium, halide, alkyl,cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl,alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl,carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl,sulfinyl, sulfonyl, phosphino, and combinations thereof.
 11. Thecompound according to claim 1, wherein the compound is selected from thegroup consisting of:


12. The compound according to claim 1, wherein A^(a) is

which may be further substituted, and wherein the substitution isoptionally fused to at least one benzo or azabenzo ring; wherein X^(a1)is selected from the group consisting of O, NR′, S, and Se; whereinY¹¹-Y^(a13) and Y^(a6)-Y^(a9) are each independently CR or N; andwherein each R and R′ is independently selected from the groupconsisting of hydrogen, deuterium, halide, alkyl, cycloalkyl,heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl,cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl,carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl,sulfonyl, phosphine, and combinations thereof.
 13. The compoundaccording to claim 1, wherein A^(b) is

which may be further substituted, and wherein the substitution isoptionally fused to at least one benzo or azabenzo ring; wherein X^(a1)is selected from the group consisting of O, NR′, S, and Se; whereinY¹¹-Y^(a13) and Y^(a6)-Y^(a9) are each independently CR or N; andwherein each R and R′ is independently selected from the groupconsisting of hydrogen, deuterium, halide, alkyl, cycloalkyl,heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl,cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl,carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl,sulfonyl, phosphine, and combinations thereof. 14.-18. (canceled)
 19. Adevice comprising one or more organic light emitting devices, at leastone of the one or more organic light emitting devices comprising: ananode; a cathode; and an organic layer, disposed between the anode andthe cathode, comprising a compound having the structure of Formula I:

wherein G^(a) has the structure

wherein G^(b) has the structure

wherein Z is selected from Si and Ge; wherein X^(a) and X^(b) areindependently selected from the group consisting of O, S, and Se;wherein Y^(a1)-Y^(a3), Y^(a6)-Y^(a9), Y^(b1)-Y^(b3), Y^(b6)-Y^(b9),Z^(a2)-Z^(a6) and Z^(b2)-Z^(b6) are each independently selected from Cor N; wherein R¹ and R² each independently represent mono, di, tri,tetra, or penta substitution, or no substitution; wherein R^(a1) andR^(b1) each independently represent mono, di, tri, or tetrasubstitution, or no substitution; wherein R^(a2) and R^(b2) eachindependently represent mono, di, or tri substitution, or nosubstitution; wherein each R¹, R², R^(a1), R^(a2), R^(b1), and R^(b2) isindependently selected from the group consisting of hydrogen, deuterium,halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy,amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl,heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile,isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphine, and combinationsthereof; wherein at least one R^(a1) is L^(a)-A^(a); wherein at leastone R^(b1) is L^(b)-A^(b); wherein A^(a) and A^(b) are eachindependently selected from the group consisting of carbazole,azacarbazole, dibenzofuran, dibenzothiophene, dibenzoselenophene,azadibenzofuran, azadibenzothiophene, azadibenzoselenophene,triphenylene and azatriphenylene which are optionally furthersubstituted, and wherein the substitution is optionally fused to atleast one benzo or azabenzo ring; and wherein L^(a) and L^(b) are eachindependently an organic linker.
 20. The device of claim 19, wherein theorganic layer is an emissive layer and the compound of Formula I is ahost.
 21. The device of claim 19, wherein the organic layer furthercomprises a phosphorescent emissive dopant, wherein the phosphorescentemissive dopant is a transition metal complex having at least one ligandor part of the ligand if the ligand is more than bidentate selected fromthe group consisting of:

wherein R_(a′), R_(b′), R_(c′), and R_(d′) may represent mono, di, tri,or tetra substitution, or no substitution; wherein R_(a′), R_(b′),R_(c′), and R_(d′) are independently selected from the group consistingof hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl,arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl,heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylicacids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl,phosphino, and combinations thereof; and wherein two adjacentsubstituents of R_(a′), R_(b′), R_(c′), and R_(d′) are optionally joinedto form a fused ring or form a multidentate ligand.
 22. The device ofclaim 19, wherein the organic layer is a blocking layer and the compoundof Formula I is a blocking material in the organic layer.
 23. The deviceof claim 19, wherein the organic layer is an electron transporting layerand the compound having Formula I is an electron transporting materialin the organic layer.
 24. The device of claim 19, wherein the device isselected from the group consisting of a consumer product, an electroniccomponent module, an organic light-emitting device, and a lightingpanel.
 25. A formulation comprising a compound having the structure ofFormula I:

wherein G^(a) has the structure

wherein G^(b) has the structure

wherein Z is selected from Si and Ge; wherein X^(a) and X^(b) areindependently selected from the group consisting of O, S, and Se;wherein Y^(a1)-Y^(a3), Y^(a6)-Y^(a9), Y^(b1)-Y^(b3), Y^(b6)-Y^(b9),Z^(a2)-Z^(a6) and Z^(v2)-Z^(b6) are each independently selected from Cor N; wherein R¹ and R² each independently represent mono, di, tri,tetra, or penta substitution, or no substitution; wherein R^(a1) andR^(b1) each independently represent mono, di, tri, or tetrasubstitution, or no substitution; wherein R^(a2) and R^(b2) eachindependently represent mono, di, or tri substitution, or nosubstitution; wherein each R¹, R², R^(a1), R^(a2), R^(b1), and R^(b2) isindependently selected from the group consisting of hydrogen, deuterium,halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy,amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl,heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile,isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphine, and combinationsthereof; wherein at least one R^(a1) is L^(a)-A^(a); wherein at leastone R^(b1) is L^(b)-A^(b); wherein A^(a) and A^(b) are eachindependently selected from the group consisting of carbazole,azacarbazole, dibenzofuran, dibenzothiophene, dibenzoselenophene,azadibenzofuran, azadibenzothiophene, azadibenzoselenophene,triphenylene and azatriphenylene which are optionally furthersubstituted, and wherein the substitution is optionally fused to atleast one benzo or azabenzo ring; and wherein L^(a) and L^(b) are eachindependently an organic linker.